1. Field of the Invention
The present invention relates to a 3D (three dimensional) display apparatus and method of a brightness modulation type (i.e., a luminance or intensity modulation type), which can show a 3D) image for a viewer by displaying a plurality of images of an object with changing the brightness of the images and overlapping the images on each other from a view point of the viewer.
2. Description of the Related Art
There is a LC (Liquid Crystal) shutter glass method or the like as a 3D display apparatus, which can show a 3D image of motion picture and can electrically rewrite the 3D) image. This LC shutter glass method shows the 3D image by inputting an image signal, which is composed of image data including parallax information obtained by shooting a picture of a 3D object from several directions, into a 2D display apparatus. A viewer or observer wears a pair of LC shutter glasses. When an odd field image is on the 2D display, the LC shutter for a right eye becomes to be able to transmit a light therethrough and the LC shutter for a left eye becomes to be able to cut off the light. On the other hand, when an even field image is on the 2D display, the LC shutter for a right eye becomes to be able to cut off the light and the LC shutter for the left eye becomes to be able to transmit the light therethrough. In this case, by displaying an image for the right eye in the odd field and displaying an image for the left eye in the even field with two images synchronized, the viewer can perceive the 3D image by watching the two images, including the parallax for the right eye and the left eye, with his eyes.
According to this LC shutter glass method, it is necessary for the viewer to use the pair of LC shutter glasses. For example, it is unnatural to use the pair of LC shutter glasses in a television conference. In physiological factors of 3D viewing, a big contradiction between (i) parallax of two eyes or congestion and (ii) focusing may happen. That is to say, although the LC shutter glass method can satisfy the parallax of two eyes and the congestion since there is a focusing face on a surface of the image, this contradiction makes the viewer's eyes so tired.
On the account, a cubic-volume method which shows the 3D image by placing a plurality of the 2D display apparatuses in front of the viewer is proposed to solve a problem about the above described contradiction between (i) the parallax of two eyes or the congestion and (ii) the focusing. The cubic-volume method can show the 3D image between two of the 2D display apparatuses by displaying a gathering of several 2D images, which are sampled to a depth direction from a view point of the viewer, on two pieces of the 2D display apparatuses which are arranged at a predetermined interval for example. According to this method, which is different from the LC shutter glass method, it is possible to ease the contradiction between (i) the parallax of two eyes or the congestion and (ii) the focusing. However, according to the cubic-volume method, it is difficult to show an object, which is placed at a middle position of the two of the 2D display apparatuses or changes its position in a great magnitude toward the depth direction from the viewer, because the several 2D images are discretely positioned in the depth direction from the viewer.
On that account, a 3D display method of a brightness modulation type is proposed, which can interpolate the interval, even if showing positions of the several 2D images are discrete, by giving a variation to the brightness of the 2D image which is shown on each of two pieces of the 2D display apparatuses. According to this brightness modulation method, it is possible to ease the contradiction between (i) the parallax of two eyes or the congestion and (ii) the focusing, and is possible to ease eyestrain or the like. Also, the brightness modulation method has an advantage, which is to decrease an amount of data in showing the 3D image, because it is possible to make the viewer perceive the object existing in the middle position of the two image surfaces three-dimensionally and further to show objects existing on a plurality of surfaces.
However, this brightness modulation method has such a problem that the 3D display apparatus cannot show the image of a semitransparent object or the image through which the viewer can watch an object at the back of the image.
To this problem, the brightness modulation method which can show the image of a semitransparent object and the image through which the viewer can watch the object at the back of the image, by overlapping and showing the images of the object on several 2D display apparatuses by using a plurality of half mirrors, is proposed by the Japanese Patent Application Laying Open NO. 2000-115812.
However, in this method, the 3D display apparatus is large in scale and is so complicated that the 3D display apparatus cannot meet general requirements of miniaturization, lightweight and cost reduction in the concerned technical field because the 3D display apparatus includes a plurality of optical elements such as half mirrors and the like.